Hello I just noticed the same issue with the yellow fungus like circles on my hatchling sulcatas I have to and it is affecting one I have isolated them and I have started treatment with Lotrimin antifungal cream it seems to be drying them out and working I just wanted to update
I have two new baby sulcatas they are around 3 months old I need help with that UVB lighting I have a 25 UVB fluorescent 18 in bulb about 12 to 14 in away is that too much UVB for them